New research by Professors Mark Harrison from the University of Warwick and Nikolaus Wolf from Humboldt University has revealed that between 1870 and 2001, the frequency of wars between states increased steadily by 2% a year on average.

“Steadily” might be overstating it, but there is a decidedly upward trend in a graph of their findings (from this paper):

What explains this increase?

Economic growth and the proliferation of borders.

The effect of borders is intuitive: more borders = more potential conflicts. Doubly so, in fact, since the researchers define wars as between separate states. A new border can thus transform a civil war, which isn’t counted, into a war between states, which is.

But why would economic growth encourage wars? Because it makes them cheaper:

In Harrison’s view, political scientists have tended to focus too much on preferences for war (the ‘demand side’) and have ignored capabilities (the ‘supply side’). Although increased prosperity and democracy should have lessened the incentives for rulers to go to war, these same factors have also increased the capacity of countries to go to war. Economic growth has made destructive power cheaper. It is also easier for modern states to acquire destructive power because they able to tax more easily and borrow more money than ever before.

Mark Harrison concluded that: ‘The very things that should make politicians less likely to want war – productivity growth, democracy, and trading opportunities – have also made war cheaper. We have more wars, not because we want them, but because we can.

In short, wars are up for the same reason that our offices aren’t paperless: progress sometimes increases supply more than it reduces demand.